Thermo-setting compositions of styrene and cinnamic acid ester of epoxide resin



Patented Aug. 5, 1958 United States Patent 2,846,410 TABLE I THERMO-SETTING COMPUSITIONS OFSTYRENE Average Melting Color Viscosity- Epoxide AND CINNAMIC ACI ESTER F EPOXIDE Ether Resin value P oiat, (Gard- (Gardirzleo Equivalent RESIN ner),max. H01) Weight Frank Armitage and Leslie George Trace, Homer-ton, 20-28 Ag-Al 225-290 London, England, assignors, by mesne assignments, to 2 3152 2 gig 332:??? The Sherwin-Williams Company, Cleveland, Ohio, a 8 1, 6004 900 corporation of Ohio 145-155 11 22-25 2, 400-4, 000

N0 Drawing. Aspplication August 26, 1954 ,Dumms Mercury method Sena! NO- 4529463 1 4035 Solution in Butyl Carbitol (mono butyl ether of diethylene Claims priority, application Great Britain iir'ri Solution in Butyl Oarbitol (mono butyl ether of (liethylene February 1954 fiiigoxide Equivalent Weight: grams of resin containing one equivalent 3 Claims. (Cl. 260-23) Reference may be had to U. S. Patent Nos. 2,541,027 Thi invention is for improvements in or relating to and 2,528,932 wherein are provided adequate directions thermo-sett'ing compositions, particularly such composifor the preparation of epoxy resins useful herein. tions as would be suitable for use in electrical insulation. A feature of the invention is that the epoxy resin may Thermo-setting resins frequently employed in electrical be modified with a minor proportion of long chain satuinsulation, such as phenolic resins, alkyd resins, urearated or unsaturated fatty acids (preferably containing and melamine-formaldehyde resins, very often blended from 12 to 26 carbon atoms in the chain) in addition to with drying oils and/ or plasticizers, are characterized by the major esterifying cinnamic acid. This may be userelatively high power factor and relatively high water abful if greater flexibility of the finished cast is required sorption. Such materials are not suitable for the insulathan that obtained by using only cinnamic acid. The tion of high-frequency coils especially if these are to practical advantages of the esters of this invention are, be used in tropical conditions. generally, a quicker speed of polymerization and the pos- Polystyrene is known to have a very low power factor sibility of obtaining harder casts at the same percentage and low water absorption characteristics, but being of styrene than with the cinnamic acid esters of unthermoplastic it is liable to distortion at elevated tem- 30 saturated p y y alcohols The cinnamic acidestersof peratures and, moreover, is brittle and difiicult to plastithese epoxy resins are useful as cross-linking agents in cize. The introduction of cross-linking agents, such as the production of thermo-setting products from vinyl divinyl benzene, is known to confer thermo-setting propcompounds, for example, styrene, for use, among other erties on the polystyrene. Polymerizable compounds purposes, for electrical insulation. Mixtures of the cinwhich are derivatives of maleic anhydride, such as diallyl namic acid esters of epoxy resins may employed and maleate, alkyd resins made from maleic and phthalic there may, in addition, be present small amounts of other anhydrides, including those resins which have been modicross-linking agents (i. e. polyfunctional compounds) fied with fatty acids and the esterification products of such as divinyl benzene, maleic-anhydfide derivatives, maleic anhydride and castor oil (with or without deallyl esters and cinnamic acid esters of saturated or uncarboxylation) have all been used for producing cross- Saturated P y y alcoholsone advantage the linked co-polymers. compositions of the present invention is that they do According to the present invention, there is provided a not require a solvent and all of the constituents of the thermo-setting composition comprising an admixture of a th rrnO-Sefififlg compositions are, on curing, present in cinnarnic acid ester or partial ester of an epoxy resin as the final product.

herein defined and a co-polymerizable monomer, It is a feature Of the invention that the co-polymeriz- The term epoxy resin as used herein means the reable monomer is styrene or a nuclear alkyl or nuclear a ti n product of a polyhydric organic compound a d halogen substituted styrene although other co-poiymeriza polyfunctional etherifying agent, particularly of a polyable monomeric Vinyl Compounds y be a hydric phenol, such as the diphenylol alkanes, and epiples of other monomers are acrylo-nitrile, methyl chlorohydrin or analogous compounds. Apreferred-class acrylate, Vinyl acetate, acena'phthylel'le and Substituted of these compounds are the glyceryl polyethers of distyrenes generally. hydric phenols, obtained by reactinga dihydric phenol, For the purposes of high frequency insulation the presuch as a diphenylol alkane, in alkaline solution with ferred monomer to be used is styrene or vinyl toluene,

epichlorohydrin. Although such resins are a complex but for alternative uses, other co-polymerizable monomixture of compounds, the main product may be repremers, such as methyl styrene, methyl methacrylate, sented by the formula: vinyl acetate, acrylo-nitrile and acenaphthylene may be where R represents the divalent hydrocarbon radical of used, preferably in admixture with the styrene. Acea dihydric phenol. naphthylene is a useful addition monomer since its rela- Exemplary of this class of ether resins is the group of tive non-volatility reduces possible volatilization losses. materials having the following general formula: Where the epoxy resins are partially esterified with O CH3 OH CH3 0 The value of n is at least one. With increasing values unsaturated fatty oil acids, particularly with conjugated of n, a range of properties are available permitting selecunsaturated fatty oil acids, it is an advantage if the said tion of desirable properties in the final product. fatty acids have been co-polymerized with a vinyl compound, such as styrene, before the esterification is carried out since less of the co-polymerizable monomer is required to form a thermosetting composition than would otherwise be required to produce a final product having the same electrical properties.

Various controlling agents may be incorporated in the composition in order to control the polymerization reaction, a controlling agent such as methyl aniline, for example, when used in amounts of up to 1% by weight of the composition appears to reduce the rate of reaction and may, in certain circumstances, obviate the formation of bubbles in the final cured product, an effect which can also be obtained by the inclusion of cobalt naphthenate in the composition; hydroquinone or similar polymerization inhibitors may be added to give storage-stability to the composition.

In order to facilitate the polymerization reaction, it is advantageous to include a peroxidic polymerization catalyst such as benzoyl peroxide, methyl ethyl ketone peroxide, tertiary butyl hydroperoxide, ditertiary butyl peroxide and tertiary butyl hydroperoxide, ditertiary butyl peroxide and tertiary butyl perbenzoate in the composition and, in some instances, it may be an advantage that the composition is partially polymerized to produce a liquid co-polymer so that the final curing time may be reduced or that the viscosity characteristics are more suitable for a particular application. Such partial prepolymerization will also reduce shrinkage when poured into the mould and reduce volatilization losses.

The preferred composition com-prises to 95% by weight of the co-polymerizable monomer, preferably from 75 to 90%, particularly in the case of styrene, the remainder of the composition being substantially the cinnamic ester.

The presence of acrylo-nitrile in the composition is, in certain circumstances, an advantage since We have found that the presence of acrylo-nitrile increases the speed of the co-polymerization reaction.

The invention also includes a method of preparing an insulated electrical winding by impregnating the winding with a composition in accordance with the present invention and heating the impregnated winding to effect a cure of the composition.

The products obtained by curing the compositions of the present invention provide a hard, tough gel of excellent mechanical and electrical properties. It is possible to use such mixtures for the embedment of electrical coils where the cured resin will be substantially free from fractures, which occasionally mar the properties of compositions which are derivatives of maleic anhydride, and from bubbles which is another source of weakness with some insulating compositions.

The following examples, in which the cobalt naphthenate solution is one containing 4% by weight of cobalt calculated as the metal, will serve to illustrate various methods of carrying the invention into effect.

Example 1 150 grams of resin B (Table 'l) and 150 grams of cinnamic acid were dissolved in 30 grams of xylene containing 1.5 grams of p-toluene sulphonic acid. The reaction mixture was refluxed for 5 /2 hours at 190- 215 C. and the water of esterification wasdistilled off azeotropically with xylene, through a Dien and Stark separator.

The xylene was finally removed by distillation under vacuum to give a hard brittle resin having an acid value of 36.

35 grams of this ester were dissolved in grams of styrene and 0.5 gram of tertiary butyl hydroperoxide and 0.1 gram of cobalt naphthenate solution were added This mixture was heated at 195 F. and, after 1 /2 hours heating, a hard gel was produced.

4 ExampleZ 200 grams resin B (Table I) 100 grams cinnamic acid 30 grams xylene 0.75 gram p-toluene sulphonic acid The above mixture was refluxed up to 210 C., with a Dien and Stark separator, for 9 hours, by which time the mixture had an acid value of 4.7. The xylene was distilled off and the molten resin poured into a tray.

25 grams of this resin was melted and dissolved in 225 grams of styrene containing 0.25 gram of hydroquinone. In the cold, this solution was somewhat opalescent though quite clear when warmed. 50 grams of this solution with 0.5 gram of tertiary-butyl hydroperoxide and 0.1 gram of cobalt naphthenate solution was heated at 190 F. for 16 hours. A hard, clear cast, free of bubbles and cracks was produced. A corresponding experiment where the tertiary-butyl hydroperoxide was replaced by benzoyl peroxide gave rise to a more rubbery cast.

Example 3 192 grams resin C (Table I) 84 grams linseed oil fatty acids 104 grams cinnamic acid 38 grams xylene 0.95 gram p-toluene sulphonic acid An esterification reaction on the above mixture was carried out in a similar manner to that described in Example 2. After 10 /2 hours reaction an acid value of 19.5 was reached. After distilling off the xylene under vacuum, the ester was dissolved in an equal weight of styrene containing 0.12 gram of hydroquinone.

20 grams of this solution were mixed with grams of styrene and 1 gram of tertiary-butyl hydroperoxide and 0.2 gram of cobalt naphthenate solution added. This was divided into two partsinto one was placed a piece of thick galvanized iron rod. At 190 F. the solution with metal gave a soft gel in 1 /2 hours and was quite hard after 4 /2 hours. The solution without the metal required longer for complete cure, but after heating overnight had become equally hard. Both casts were quite clear and substantially free from cracks or bubbles.

Other modes of applying the principle of this invention may be employed instead of those specifically set forth above, changes being made as regards the details herein disclosed, provided the elements set forth in any of the following claims, or the equivalent of such be employed.

We claim:

1. A thermosettable composition comprising an admixture of an ester of an acid selected from the group consisting of cinnamic acid and mixtures of cinnamic acid and at least one long chain fatty acid containing from 12 to 26 carbon atoms in the chain, and a polyglycidyl Y 'polyether resin having a 1,2-epoxide equivalent weight of from about 225 to 4,000; and a vinyl monomer se lected from the group consisting of styrene, nuclear alkyl substituted styrene, and nuclear halogen-substituted styrene, the amount of said vinyl monomer being from about 5% to about 95% of the combined weight of said monomer and said ester.

2. A composition in accordance with claim 1 which is additionally characterized by the presence therein of up to 1% by weight of the composition of cobalt naphthenate to obviate the formation of bubbles in the thermoset product.

3. A composition in accordance with claim 1 in which the vinyl monomer constitutes from 75% to of the combined weight of said monomer and said ester.

References Cited in the file of this patent UNITED STATES PATENTS 2,318,959 Muskat et a1 May 11, 1943 2,320,536 Pollack June 1, 1943 2,575,440 Bradley Nov. 20, 1951 2,660,563 Banes et al Nov. 24, 1953 

1. A THERMOSETTABLE COMPOSITION COMPRISING AN ADMIXTURE OF AN ESTER OF AN ACID SELECTED FROM THE GROUP CONSISTING OF CINNAMIC ACID AND MIXTURES OF CINNAMIC ACID AND AT LEAST ONE LONG CHAIN FATTY ACID CONTAINING FROM 12 TO 26 CARBON ATOMS IN THE CHAIN, AND A POLYGLYCIDYL POLYMER RESIN HAVING A 1,2-EPOXIDE EQUIVALENT WEIGHT OF FROM ABOUT 225 TO 4,000; AND A VINYL MONOMER SELECTED FROM THE GROUP CONSISTING OF STYRENE, NUCLEAR ALKYL SUBSTITUTED STYRENE AND NUCLEAR HALOGEN-SUBSTITUTED STYRENE, THE AMOUNT OF SAID VINYL MONOMER BEING FROM ABOUT 5% TO ABOUT 95% OF THE COMBINED WEIGHT OF SAID MONOMER AND SAID ESTER. 